Fertilizers are responsible for over half of global food production, but there are areas in world with nutrient deficiency and other areas of nutrient excess.
Managing mineral plant nutrients requires careful application of science and skill to meet production, environmental, and social goals.

Thursday, September 13, 2012

What About the Water?

Water... handle with care

Of course farmers use a lot of water... they are shipping water (in the form of food) to you

Agriculture is the largest user of fresh water in the world and as demand grows for more food production, conflicts regarding water use are inevitable. In some areas, additional investment in irrigation and water supplies may provide room for further expansion of irrigated cropland. However in most areas of western North America, water is no longer in abundant supply and ferocious arguments erupt over water allocation. Since new supplies of irrigation water appear unlikely, there is significant incentive to improve water use efficiency. The pressure on the agricultural industry to carefully conserve water resources will certainly intensify.

Soil water during the drying process

Water uptake and plant nutrient absorption are closely related. When plant roots take up water, dissolved nutrients are carried to the root surface. When water uptake is restricted, the delivery of nutrients to the root also slows down. As the soil dries and the films of water between the particles shrink, the processes of mass flow and diffusion that bathe the roots with nutrients eventually come to a halt.

An impaired root system hinders water and nutrient uptake

Healthy
roots and water use

An
important step towards improving water use efficiency is to encourage healthy
plant roots. Maintaining proper soil conditions will enhance the volume of soil
that roots explore. For example, a soil that has a compacted zone or a hard pan
will present a barrier to plant roots and restrict their use of moisture deeper
in the soil profile. Similarly, when subsoil acidity is not addressed, plant
growth is stunted and roots cannot grow deep into the soil to utilize water and
nutrients.

Plants grown with
adequate nutrition typically have larg­er tops and root systems compared with
crops grown with an inadequate nutrient supply. These well-fertilized plants
are generally larger and may have greater water loss (tran­spiration), but a
lower transpiration ratio. In other words, the healthy plant may use more
water, but will generally produce larger yields. This translates into more
yield per gallon of water extracted from the soil. Another way to say this is
that greater water use efficiency results from proper plant nutrition.

How
much water is in our food?

It
seems like there is rarely enough water in western North America to meet
everybody’s needs. Especially after several years of prolonged drought in many
areas, farmers are stressed to learn that there may be insufficient water to
grow their crops.

The amount of water required to grow a crop

A common cry from the
urban areas is that agriculture uses more than its “fair share” of water. Some
estimates have been made that more than 80% of developed water is go­ing to
agriculture in many areas. Attention is drawn to the fact that agriculture
loses too much water through cracks, seepage, and evaporation from the miles of
canals and pipelines. These losses should be addressed when financing is
available.

Most
consumers do not appreciate the large amount of water required to grow plants.
A poorly understood concept is that a huge amount of water is indirectly
delivered to cities in the form of food. A report by the Water Education
Foundation documented the amount of water required to produce various foods in
the western U.S. Their basic ap­proach was to divide average water use
(evapotranspiration) by average yields to determine the gallons of water per
pound of food produced. Since some of the water delivered to a farm is
unavoidably lost as deep percolation, runoff, or soil moisture storage, the irrigation
efficiency was assumed to be 70%.

Using
a typical 2,300-calorie menu proposed by the U.S. Department of Agriculture,
the following meal was con­structed and the gallons of water required to
produce that particular food item are shown.

The amount of water required to grow our daily food

Do farmers use a lot of water?Yes… and we all benefit tremendously from
their produc­tivity. The water may not only come from our faucets, but it also
comes to us in every bite we take.

Proper plant nutrition is a vital key to achieving efficient use
of water. Nitrogen deficiencies have an impact on the ability of a crop to convert
available water into yield. Phos­phorus is important in stimulating
seedling root develop­ment. This helps the plant explore more soil, increasing
the recovery of nutrients and water. Potassium is often referred to as
the regulator nutrient, influencing the water dynamics in plants. Nutrients
play an essential role in allowing plants to convert water and sunshine into
food.

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About Me

I am a soil scientist with interest in managing plant nutrients in the best way possible. I am fortunate to be able to work in research and education to be able to accomplish this goal.
After receiving a PhD in Soil Science at the University of California (Riverside), I worked as a Research Scientist for the U.S. government, as a Professor of Soil Science, and now I work for a not-for-profit institution. It's been a wonderful experience!